Why have a blood test to diagnose hay fever

Itchy, watery eyes, sneezing and nasal congestion are some common symptoms you may experience if you’re suffering from hay fever. 

Here’s how and why a blood test for hay fever can provide an accurate diagnosis and what treatment options are advised.

Understanding hay fever

“Hay fever, also known as allergic rhinitis, occurs when the mucosal lining within the nasal passages reacts to commonly encountered inhaled allergens,” explains Dr Pieter de Waal, a paediatric asthma and allergy specialist at Mediclinic Panorama. “Hay fever is diagnosed clinically by a medical doctor through a careful history of symptoms present and testing, either through skin prick tests or a blood test for antibodies against commonly inhaled allergens.”

These allergens include pollen from grasses, weeds, trees and pets – commonly cats and dogs – house dust mites, cockroaches and mould spores. Symptoms usually worsen in the spring and early summer months when the pollen count is at its highest.

“Testing what you are allergic to is always recommended in all hay fever sufferers so that successful avoidance strategies can be implemented,” says Dr de Waal. While hay fever cannot be cured, such strategies can help with effective management of symptoms.

Testing options for hay fever

“A blood test checks for allergic antibodies (known as Immunoglobulin E or IgE) that the susceptible immune system produces in response to commonly encountered inhaled allergens,” Dr de Waal explains. Increased levels of IgE antibodies directed towards inhaled allergens, indicate a possible respiratory allergy. However, in some cases, high IgE levels indicate the possibility of a parasitic infestation, especially involving the gastrointestinal tract.

 “A blood test for hay fever is very accurate and, in most instances, will effectively diagnose your inhalant allergy,” says Dr de Waal.

In diagnosing hay fever, a skin prick test may also be considered, he continues. “A skin prick test may be performed by some specialists during the actual allergy consultation. This will almost immediately and accurately diagnose commonly encountered inhalant allergens and can be performed as an alternative to blood testing. A needle prick to draw blood is therefore not necessary when skin prick testing is performed.”

I tested positive for hay fever – now what?

Once you know your triggers you can better manage your exposure to them. “Your doctor should decide on the appropriate avoidance strategies of the allergen to which you have tested positive to,” says Dr de Waal. While you’re unlikely to completely escape your allergens completely, you can limit your exposure to them.

“For most inhalant allergens, allergen immunotherapy – monthly injections for about three years – has been shown to effectively treat symptoms of hay fever,” Dr de Waal adds. By injecting tiny amounts of the allergens over time, your body can get used to the allergens that cause your symptoms, decreasing your need for medication.

However, medications used separately or together may often be the first port of call. Medicine for hay fever usually includes a nasal spray with or without a systemic antihistamine. Intranasal corticosteroid nasal sprays address the inflammation caused by environmental allergens, and apart from immunotherapy, are the only effective treatment available for hay fever. Oral antihistamines may address runny, itching, and sneezing problems, but do not address the inflammation caused by an allergen.

Your doctor may also recommend nasal saline rinses to wash away the mucous from your nasal passages. To really be effective, hay fever sufferers are encouraged to use their medicine, especially their nasal spray on a regular and ongoing basis, during periods when they have symptoms.